Generator packaging arrangement

ABSTRACT

An accessory system includes a generator integrally mounted with an accessory gearbox such that a drive gear of the generator is in meshing engagement with the geartrain.

The present disclosure claims priority to U.S. Provisional Patent Application No. 61/284,451, filed Dec. 18, 2009; U.S. Provisional Patent Application No. 61/284,452, filed Dec. 18, 2009; and U.S. Provisional Patent Application No. 61/284,453, filed Dec. 18, 2009.

BACKGROUND

The present disclosure relates to a generator packaging arrangement which facilitates heavier generator installation onto smaller gearboxes without adversely affecting the gearbox weight yet maintains desired generator design features.

As modern commercial aircraft transition to a more electric architecture, relatively larger generators are being installed into smaller engine nacelles. These relatively heavier generators are also being mounted to smaller accessory gearboxes. As generator weight begins to account for the majority of the accessory gearbox load, specific design changes to the accessory gearbox may be necessary to accommodate the generator. Also, as the generator is typically cantilever mounted off the accessory gearbox, heavier generators may result in increased overhung bending moments which require increased accessory gearbox housing wall thicknesses and weight.

SUMMARY

An accessory system according to an exemplary aspect of the present disclosure includes a generator integrally mounted with an accessory gearbox such that a drive gear of the generator is in meshing engagement with the geartrain.

A generator according to an exemplary aspect of the present disclosure includes a drive shaft assembly supported within a generator housing. A drive gear, a main generator power section and a permanent magnet generator (PMG) driven by the drive shaft assembly, the permanent magnet generator (PMG) mounted opposite the drive gear relative the main generator power section.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows:

FIG. 1 is a general perspective view of a generator which mounts to an aircraft accessory gearbox;

FIG. 2 is a schematic view of the generator connected to the accessory gearbox; and

FIG. 3 is an electrical schematic of the generator.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a generator 20 which mounts to an aircraft accessory gearbox AG (illustrated schematically) though a drive gear 20G which rotates about a generator axis of rotation A to form an accessory gearbox system 10. In the disclosed, non-limiting embodiment, an Integrally Mounted Gearbox Generator and a 2-Pole Integrally Mounted Gearbox Generator may be utilized. It should be understood that the generator may alternatively be a starter generator or other such machines. It should be appreciated that a 2-pole machine operates at a relatively higher speed and may have a relatively larger core than a 4-pole machine, however a 4-pole machine provides relatively greater rotor mechanical strength and may have relatively greater reliability. It should be appreciated that any pole count design generator may be integrated with an accessory gearbox AG as described herein.

The generator 20 includes a generator housing 20H which defines a mounting flange 20F that is axially outboard of the drive gear 20G relative to the accessory gearbox AG. The drive gear 20G extends through a side area of the generator housing 20H at a scallop 21 to mesh with the geartrain G within the accessory gearbox AG. The drive gear 20G is integral with the geartrain G of the accessory gearbox AG. That is, the drive gear 20G is part of the geartrain G such that gears downstream of the drive gear 20G are utilized to drive associated accessory systems.

With reference to FIG. 2, the generator 20 generally includes a main generator power section 22, an exciter 24, a rectifier assembly 26 and an optional permanent magnet generator (PMG) 28. The generator 20 provides a packaging arrangement in which the heaviest portions of the generator 20 such as the main generator power section 22 are located generally adjacent to the gearbox mounting flange 20F and at least partially within the accessory gearbox AG.

The main generator power section 22 provides alternating current (AC) power to an aircraft electrical bus (not shown). The exciter 24 provides excitation current to the field of the main generator power section 22. The rectifier assembly 26 provides conversion of exciter armature alternating current (AC) power into direct current (DC) power for the main field portion of the main generator power section 22. If generator self-excitation is required, the generator 20 will also include the PMG 28 which provides AC power to the generator control unit for generator field excitation power.

The main generator power section 22, the exciter 24 and the optional PMG 28 are mounted on a common rotor shaft assembly 30 which is supported within the generator housing 20H of the generator 20 by main bearings 34A, 34B. In one non-limiting embodiment, the gearbox mounting flange 20F and the main generator power section 22 are axially located between the main bearings 34A, 34B, the exciter 24 is mounted on the rotor shaft assembly 30 axially outboard of the second main bearing 34B. The optional PMG 28 may either be axially outboard of the main generator power section 22 or opposite the generator drive gear G of the main generator power section 22 and the exciter 24 is mounted on the same side of the gearbox as the main generator power section 22.

The rectifier assembly 26 is mounted internal to the rotor shaft assembly 30. The rectifier assembly 26 typically includes three or six discrete diodes 36 arranged such that they provide rectification of the AC power developed by the exciter 24. The DC output of the rectifier assembly 26 is fed into the main field of the main generator power section 22.

Location of the diodes 36 internal to the rotor shaft assembly 30 provides an efficient use of space within the generator 20. The discrete diodes 36 and associated electrical connections are arranged in a compact fashion such that the diodes 36 readily will fit within a diode housing 38 fit into the rotor shaft assembly 30. The diode housing 38 provides support to the diodes 36, electrical connections and insulation of the various electrical circuits. It should be understood that additional components may be provided within the diode housing 38 to provide support and electrical insulation.

With reference to FIG. 3, the three phase output of the exciter 24 is connected to the rotating rectifier AC connections and the DC output of the rectifier assembly 26 is connected to the main generator power section 22. The AC output of the exciter 24 is provided to the rectifier assembly 26 via lead wires which extend inward from the exciter 24 to the rectifier assembly 26. The lead wires are attached to the individual windings within the exciter 24 and connected individually to the three AC circuits within the rectifier assembly 26. The DC output of the rectifier assembly 26 is connected to the generator power section 22 via wires or bus bars which extend axially and radially from the rectifier assembly 26 to the generator power section 22.

The generator 20 arrangement disclosed herein also allows a resolver (not shown) to be packaged therein. The resolver is a rotary device that includes a rotor and a stator. The resolver rotor is mounted to the rotor shaft assembly 30 and the stator is mounted to the housing. The resolver provides an electrical signal that can be used by a control unit for the generator or starter/generator to identify the position of the generator or starter/generator rotor relative to the generator housing 20H. The exact construction of the resolver rotor and stator varies, and may consist of a wound rotor or a solid rotor. The resolver stator consists of one or more windings which couple with the rotating magnetic field produced by the resolver rotor. This coupling produces an electrical signal within the stator windings that is fed to the control unit to determine rotor position. Rotor position information is used by the control unit to determine the appropriate control signals that must be applied to the generator or starter/generator to achieve proper operation.

The generator 20 provides a packaging arrangement in which the heaviest portions of the generator 20 are located close to the gearbox mounting flange 20F. This minimizes the overhung moment that must be reacted by the accessory gearbox AG and allows both the generator housing and accessory gearbox housings to be lighter. This packaging arrangement also minimizes housing and shaft/bearing weight between the generator and gearbox as they are share components.

It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting.

It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.

Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.

The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason, the appended claims should be studied to determine true scope and content. 

1. An accessory system comprising: an accessory gearbox which includes a geartrain; and a generator integrally mounted with said accessory gearbox such that a drive gear of said generator is in meshing engagement with said geartrain.
 2. The accessory system as recited in claim 1, wherein said geartrain includes a first gear in meshed engagement with said drive gear.
 3. The accessory system as recited in claim 1, wherein said geartrain includes a first and a second gear which are both in meshed engagement with said drive gear.
 4. The accessory system as recited in claim 1, wherein said geartrain is drivable with said drive gear disconnected from said generator.
 5. The accessory system as recited in claim 1, further comprising: a generator housing which defines a scallop, said drive gear extends through an opening formed through said scallop.
 6. The accessory system as recited in claim 5, further comprising a mounting flange defined by said generator housing, said mounting flange axially located adjacent to a main generator power section.
 7. The accessory system as recited in claim 5, further comprising a drive shaft assembly supported within said generator housing, said drive gear driven by said drive shaft assembly.
 8. The accessory system as recited in claim 7, further comprising an exciter driven by said drive shaft assembly, said exciter axially on a side of said drive shaft assembly as main generator power section driven by said drive shaft assembly.
 9. A generator comprising: a generator housing; a drive shaft assembly supported within said generator housing; a drive gear driven by said drive shaft assembly; a main generator power section driven by said drive shaft assembly; and a permanent magnet generator driven by said drive shaft assembly, said permanent magnet generator mounted opposite said drive gear relative to said main generator power section.
 10. The generator as recited in claim 9, further comprising: an exciter driven by said drive shaft assembly, said exciter axially on a same side of said drive shaft assembly as said main generator power section relative to said drive gear.
 11. The generator as recited in claim 9, wherein said generator housing defines a scallop, and said drive gear extends through an opening formed through said scallop.
 12. The generator as recited in claim 9, further comprising a mounting flange defined by said generator housing, said mounting flange axially located adjacent to said main generator power section. 